What does forward annotation of timing information mean?

[p_shinde]

frenz,

can anyone explain wat exactly forward annotation of timing information means?? how it differs from back annotation..........

thanks
prasad

 

[wwfhm2002]

SDF

forward annotation is annotate current netlist timing information as a guide for next step for timing optimization.

backward annotation is for timing verification.

 

[bbcallpzx]

SDF

Forward annotation is used to guide the P&R and clock tree insert, it is not very accurate cos the cell delay and net delay are estimated based on the models, after p&R tools can calculate the net and cell delay from the real circuit, it tells the timing more accurate and this is called the back annotation.